Magnetic center holder for a workshop compass



Feb. 19, 1957 w. WURSCH 2,731,582

MAGNETIC CENTER HOLDER FOR A WORKSHOP COMPASS Filed Aug. 30, 1955 United States Patent g 7 2,78 1,582 Pate'nted F ebr 19,. .195 7 MAGNETIC CENTER HOLDER FORA WORKSHOP COMPASS.

The present invention relates to a magnetic center holder for a workshopcompass.

It hasalready been proposed to hold-one leg ofaworkshop compass in the center of the circle to be described by-means of a magnetic center holder. The known center holders. have a holder pad provided with a permanent magnet, in which pad the leg of the compass is journalled without play, e. g. in a bore or with a ball joint. If it is desired to scribe a circle by means of the compass on an iron sheet or to guide a cutter torch in a circle, the holder pad is placed on the desired spot of the sheet metal where it holds fast magnetically on the same. With the known center holders the holder pad must resist all forces tending to move the centered leg of the compass out of its position. Consequently it is comparatively large, heavy and expensive, because its magnetic holding force on an iron sheet amounts to e. g. 25 kilograms.

The present invention has the primary object of providing a magnetic center holder which is smaller, handler and less expensive than the center holders hitherto known.

It is another object of the invention to provide a mag netic center holder the magnetic system of which is substantially relieved of lateral forces applied to the com pass in operation and which accordingly requires a magnetic holding force of the order of magnitude of 1.5 or 2 kilograms only.

It is yet another object of the invention to provide a magnetic center holder which dispenses with the involved centering required for certain known holder pads by the aid of markings on the circumference thereof.

It is moreover an object of the invention to provide a magnetic center holder which is operative even with thin non-magnetizable sheet metal on a magnetizable table top.

With these and other objects in view I provide a magnetic center holder for a workshop compass, comprising in combination: a holder pad having at least one permanent magnet, a leg of the workshop compass having a point projecting beyond the underside of the said pad in the rest position, and resilient means connecting the said leg to the said pad universally movably.

When in the center desired a small recess (punch mark) is made in the iron sheet by means of a center punch, and the point of the center leg is inserted into the same and the holder pad is pressed onto the iron sheet, the said resilient means are loaded and press the point into the recess. A lateral pull on the center leg is then taken by the punch mark, and not, or to a small extent only, by the holder pad. For the retaining of the point in the punch mark, however, a much smaller force sufiices than for securing the holder pad against being shifted laterally, so that the latter can be made much smaller and accordingly more handy and less expensive than hitherto, e. g. with a holding force of only 1.5 to 2 kilograms.

These and other objects and features of my said invention will be clearly understood from the following description of a preferred embodiment and some modifications thereof given by way of example with reference to the accompanying drawings, in which:

Fig. '1 is an elevation partly in section ofcne-embodiment, and. g I

Figs.' 2 and '3l'are sectional elevations of modifications ofdetailsof-Fi'g'. I.

The holder pad 1 consists of anannular permanent magnet 2 the poles of which are denoted N and S, and of a bushing 3 mounted centrally therein, which may consist of steel or alternatively of a non-magnetizable material;

The leg of 'thisworkshop compass formed by a pin 4 is. universally. movable in this hushing3, andis connected therewith by a light conical coiled spring 5 only. The upper end'of, this coiled springis retained in a groove 6 of the bushing 3, audits-lower end is retained in a groove 7 io'fI-the pin-4. In the restposition illustrated, i. e. with the spring,relaxed,1 the point 80f the pin 4' protrudes beyond. the holder pad 1., At its upper end, the pine is provided with a head 9,, in the horizontal bore IQ of which a. compass rodlll isslidable, and can be arrested by means ofascrew I6. At oneend of the compass rod a merely diagrammatically indicated cutter head 12 of an oxy-acetylene cutting torch (otherwise not shown) is mounted.

In order to cut out of the iron sheet 13, which lies on the table top 14, a circular piece, the center of the circle is marked at 15 by means of a center punch. When now the point 8 is inserted into the punch mark 15 and the holder pad 1 is pressed on to the iron sheet, the pad sticks to the latter, and the compressed spring 5 forces the point 8 firmly into the recess formed by the punch mark. Lateral forces applied to the leg 4 of the compass when guiding the cutter head round are not transmitted to the holder pad 1, but are taken by the recess 15.

The holder pad need not even lie accurately co-axially to the pin 4. The involved centering required for certain known holder pads by the aid of marking provided on its circumference is dispensed with.

The leg 4 of the compass has to be arranged by no means centrally on the holder pad 1, and the latter may have any shape desired.

According to the modification illustrated in Fig. 2, the holder pad may be provided with several, for example horseshoe-shaped, magnets 17 which are somehow fixedly connected to one another, e. g. by being embedded firmly in a body 18 consisting of an artificial substance.

Instead of a compression spring 5, obviously an appropriately arranged tension spring could be used. Alternatively, according to Fig. 3, a comparatively thick bushing 19 of rubber, e. g. foam rubber, could be connected outside to the holder pad 1, and inside to the pin 4. In this case, small lateral forces are transmitted to the holder pad though, but essentially the same beneficial effect could be attained as with the other two embodiment-s.

The device illustrated can, by the way, be used also for the scribing, cutting or the like of non-magnetizable sheet metal. When for example the table top 14 consists of iron and the sheet metal 13, consisting e. g. of copper, is thin, the holder pad will likewise adhere firmly to the sheet metal.

While I have herein described and illustrated in the accompanying drawing what may be considered typical and particularly useful embodiments of my said invention, I wish it to be understood that I do not limit myself to the particular details and dimensions described and illustrated, for obvious modifications will occur to a person skilled in the art.

What I claim as my invention and desire to secure by Letters Patent, is:

1. A magnetic center holder for a workshop compass, comprising in combination: a holder pad having at least one permanent magnet and defining a passage having an axis, a leg of the workshop compass having a point and extending through said passage and being movable in said passage in all directions relative to the axis of said passage, and resilient means connecting the said leg to the said pad, the said point projecting beyond the underside of the said pad in the rest position.

2. A magnetic center holder for a workshop compass, as claimed in claim 1, said resilient means comprising a coiled spring arranged co-axially with the said point and attached at one end to the said pad and at the other end to the said leg. I

3. A magnetic center holder for a workshop compass, as claimed in claim 1, said resilient means comprising a rubber-like elastic bushing disposed in said passage and attached outside to the said pad and inside to the said leg.

4. A magnetic center holder for a Workshop compass, comprising in combination: a holder pad having an annular magnet and a bushing arranged centrally in the ranged co-axially with the said point and attached at its lower end to the said leg and at its upper end in the said circular groove.

5. A magnetic center holder for a workshop compass as claimed in claim 4, together with clamping means arranged on the said leg adapted to hold and clamp a shiftable compass rod.

6. A magnetic center holder for a workshop compass, comprising in combination: a holder pad, said holder pad defining a passage having an axis, a plurality of magnets embedded in an artificial substance in the said holder 7 pad, a leg of the workshop compass extending through said magnet defining a bore having an axis, said bushing having a circular groove near the upper end of its bore, a leg of the compass passing with ample clearance through the bore of the said bushing and being movable relative to the axis of said bore, in all directions, in said bore and having a point projecting beyond the underside of the said pad in the rest position, and a coiled spring arsaid passage and being movable in all directions relative to saidaxis in said passage and having a point projecting beyond the underside of the said pad in the rest position, and resilient means connecting the said leg to the said pad.

References Cited in the file of this patent UNITED STATES PATENTS 2,424,286 Robbins July 22, 1947 2,505,236 Dooley Apr. 25, 1950 2,607,990 Payamps Aug. 26, 1952 2,737,720 Kaser Mar. 13 1956 

